/Engine/Source/Runtime/Engine/Public/AnimationRuntime.h
This blends in local space
static void BlendPosesTogetherPerBone ( [TArrayView](API\Runtime\Core\Containers\TArrayView)< const [FCompactPose](API\Runtime\Engine\FCompactPose) > SourcePoses, [TArrayView](API\Runtime\Core\Containers\TArrayView)< const [FBlendedCurve](API\Runtime\Engine\Animation\FBlendedCurve) > SourceCurves, const [IInterpolationIndexProvider](API\Runtime\Engine\IInterpolationIndexProvider) * InterpolationIndexProvider, [TArrayView](API\Runtime\Core\Containers\TArrayView)< const [FBlendSampleData](API\Runtime\Engine\Animation\FBlendSampleData) > BlendSampleDataCache, [FCompactPose](API\Runtime\Engine\FCompactPose) & ResultPose, [FBlendedCurve](API\Runtime\Engine\Animation\FBlendedCurve) & ResultCurve )